System and method for production of crude argon by cryogenic rectification of air

Abstract

A system and method for producing argon that uses a higher pressure column, a lower pressure column, and an argon column collectively configured to produce nitrogen, oxygen and argon products through the cryogenic separation of air. The present system and method also employs a once through argon condensing assembly that is disposed entirely within the lower pressure column that is configured to condense an argon rich vapor stream from the argon column against the oxygen-enriched liquid from the higher pressure column to produce an argon liquid product. The control system is configured for optimizing the production of argon product by ensuring an even flow split of the oxygen-enriched liquid is distributed to the argon condenser cores and by adjusting the flow rate of the argon removed from the argon condensing assembly to maintain the liquid/vapor balance in the argon condensing assembly within appropriate limits.

What is claimed is: 
     
       1. A method for producing crude argon by cryogenic rectification of a feed air stream comprising the steps of:
 (a) compressing and purifying the feed air stream; 
 (b) directing a portion of the compressed and purified feed air stream into a higher pressure column configured to produce an oxygen-enriched liquid and a nitrogen-rich overhead stream by cryogenic rectification within the higher pressure column; 
 (c) directing the nitrogen rich overhead stream from the higher pressure column to a lower pressure column configured to produce an oxygen product stream and a nitrogen-rich stream by cryogenic rectification within the lower pressure column; 
 (d) directing an argon-oxygen-containing stream from within the lower pressure column to an argon column configured to produce an argon-rich vapor stream and an argon-oxygen containing liquid by cryogenic rectification within the argon column; 
 (e) recycling the argon-oxygen containing liquid from the argon column to the lower pressure column; 
 (f) directing the argon rich vapor stream from the argon column to an argon condensing assembly disposed within the lower pressure column; 
 (g) directing a flow of the oxygen-enriched liquid from the higher pressure column to the argon condensing assembly disposed within the lower pressure column; 
 (h) condensing the argon rich vapor stream against the entire flow of the oxygen-enriched liquid from the higher pressure column to produce a crude argon-rich liquid stream and a partially vaporized oxygen-rich stream; 
 (i) releasing the partially vaporized oxygen-rich stream from the argon condensing assembly into the lower pressure column; and 
 (j) removing the crude argon-rich liquid stream from the argon condensing assembly; 
 wherein the flow of the oxygen-enriched liquid from the higher pressure column to the argon condensing assembly is sufficient to keep surfaces of the argon condensing assembly wetted and prevent the argon condensing assembly from boiling to dryness. 
 
     
     
       2. The method of  claim 1  further comprising the step of returning a portion of the crude argon-rich liquid stream to the argon column as reflux. 
     
     
       3. The method of  claim 1  further comprising the step of adjusting a flow rate of the crude argon-rich liquid stream removed from the argon condensing assembly to maintain a liquid/vapor balance of the partially vaporized oxygen-rich stream in the argon condensing assembly. 
     
     
       4. The method of  claim 1  wherein the argon condensing assembly comprises a once-through argon condenser core. 
     
     
       5. The method of  claim 1  wherein the argon condensing assembly comprises two or more once-through argon condenser cores. 
     
     
       6. The method of  claim 5  further comprising the step of adjusting a flow rate of the crude argon-rich liquid stream removed from the argon condensing assembly to maintain a liquid/vapor balance of the partially vaporized oxygen-rich stream in each of the argon condenser cores. 
     
     
       7. The method of  claim 5  further comprising the step of adjusting the flow of the oxygen-enriched liquid from the higher pressure column to the argon condensing assembly such that an even flow split of the oxygen-enriched liquid is distributed to the two or more argon condenser cores and to ensure sufficient liquid is present to keep surfaces of the argon condenser cores wetted. 
     
     
       8. A system for producing a crude argon product by cryogenic rectification of a feed air stream comprising:
 a source of compressed and purified feed air; 
 a higher pressure column configured to produce an oxygen-enriched liquid and a nitrogen-rich overhead stream by cryogenic rectification of a portion of the compressed and purified feed air within the higher pressure column; 
 a lower pressure column configured to receive the nitrogen rich stream from the higher pressure column and produce an oxygen product stream and a nitrogen-rich product stream or waste stream by cryogenic rectification within the lower pressure column; 
 an argon column operatively coupled to the lower pressure column and configured to receive an argon-oxygen-containing stream from the lower pressure column and produce an argon-rich vapor stream and an argon-oxygen containing liquid by cryogenic rectification within the argon column, wherein a portion of the argon-oxygen containing liquid is recycled from the argon column to the lower pressure column; and 
 an argon condensing assembly disposed within the lower pressure column and configured to receive the argon rich vapor stream from the argon column and to receive the oxygen-enriched liquid from the higher pressure column and to condense the argon rich vapor stream against the entire flow of the oxygen-enriched liquid from the higher pressure column to produce a crude argon-rich liquid stream and a partially vaporized oxygen-rich stream; the argon condensing assembly is further configured to release the partially vaporized oxygen-rich stream into the lower pressure column; 
 at least one control valve disposed upstream of the argon condensing assembly and configured to control the flow of the oxygen-enriched liquid from the higher pressure column to the argon condensing assembly, wherein the flow of the oxygen-enriched liquid from the higher pressure column to the argon condensing assembly is sufficient to keep surfaces of the argon condensing assembly wetted and prevent the argon condensing assembly from boiling to dryness; and 
 wherein a portion of the crude argon-rich liquid stream is extracted from the argon condensing assembly as the crude argon product. 
 
     
     
       9. The system of  claim 8  wherein a portion of the crude argon-rich liquid stream is recycled back to the argon column as reflux. 
     
     
       10. The system of  claim 8  further comprising another control valve disposed downstream of the argon condensing assembly and configured to control the flow of the crude argon-rich liquid stream removed from the argon condensing assembly to maintain a liquid/vapor balance of the partially vaporized oxygen-rich stream in the argon condensing assembly. 
     
     
       11. The system of  claim 8  wherein the argon condensing assembly comprises a once-through argon condenser core. 
     
     
       12. The system of  claim 8  wherein the argon condensing assembly comprises two or more once-through argon condenser cores. 
     
     
       13. The system of  claim 12  further comprising another control valve disposed downstream of the argon condensing assembly and configured to control the flow of the crude argon-rich liquid stream removed from the argon condensing assembly to maintain a liquid/vapor balance of the partially vaporized oxygen-rich stream in the argon condensing assembly.